How many atoms are in 163 g of calcium?

Avogadro's number represents the number of units in one mole of any substance. This has the value of 6.022 x 10^23 units / mole. This number can be used to convert the number of atoms or molecules into number of moles.

163 g Ca (1 mol / 40.08 g) (6.022 x 10^23 atoms / 1 mol) = 2.45 x10^24 atoms Ca